Technical Field
The present disclosure relates to a needle-equipped outer tube in which a needle of a syringe is directly joined to a distal end of an outer tube of the syringe in advance, and a method of manufacturing the needle-equipped outer tube.
Background Art
In some syringes having a small volume used for insulin administration or vaccination, a needle-equipped outer tube in which a needle of the syringe is directly joined to the distal end of the outer tube of the syringe in advance is used. As a method of manufacturing such a needle-equipped outer tube, a method of joining a needle to the distal end of an outer tube with an adhesive or the like, a method of joining a needle to the distal end portion of an outer tube by insert molding, and a method of joining a needle to an outer tube by thermal welding are known (see, JP 2005-342100 A). Further, a method of pressingly inserting a cylindrical joint member, which is interpositioned between a needle and an outer tube, into the outer tube to assemble together the needle, the outer tube, and the joint member is known (see JP 2004-154210 A).
When using such a joint member, it is preferable to use a method of thermally welding the joint member to an outer tube such that, using a joint member having a tapered portion in which the outer diameter decreases from the distal end side toward the proximal end side and an outer tube including a distal end connecting section having a tapered hollow configured to receive the tapered portion of the joint member, the tapered portion is thermally welded to the tapered hollow with the joint member pressed to the outer tube toward the proximal end side of the joint member. In a thermal welding step, the entire contact surface between the joint member and the outer tube need not be thermally welded, if a thermally welded section having an annular shape is formed. In this case, a portion of the outer tube making contact with the joint member includes a non-thermal-weld section which is not heated above the softening point and is not thermally welded to the joint member.
Further, in the thermal welding step, when the entire joint member is heated above a certain degree, a distal end portion of the joint member which is not yet inserted in the tapered hollow of the outer tube softens and deforms, and thereby may increase its diameter to be larger than the inner diameter of the opening of the tapered hollow. When such deformation occurs, the deformed portion cannot advance into the tapered hollow. This makes it difficult to perform thermal welding between the surfaces of the tapered portion and the tapered hollow which are in pressed contact with each other, and thus to improve sureness of welding between the joint member and the outer tube. For this reason, it is preferable that a portion of the joint member not close to the distal end, for example a middle section, is sufficiently heated to be thermally welded in a reliable manner, but the heated area is restricted to avoid softening of the distal end portion of the joint member. Therefore, the portion of the outer tube making contact with the joint member includes a portion which makes contact but is a non-thermal-weld section. Another problem is that a portion which makes contact but is a non-thermal-weld section causes a crack after the needle-equipped outer tube is manufactured.